Tube forming machine

ABSTRACT

A machine or device for forming tubes or the like includes one or more cables or other elongated flexible members. An expanding forming device is positioned at an end of the cables, and the cables are inserted into a tube that is to be formed. The expanding device expands outwardly, and tension is placed on the cables to pull the cables through the tubes. This causes the tubes to be permanently deformed outwardly to a larger outer diameter.

CLAIM OF PRIORITY

This application claims the benefit of U.S. Provisional Application No. 61/589,021 filed on Jan. 20, 2012, entitled, TUBE FORMING MACHINE, the entire contents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

Metal tubing is commonly used in a variety of components or devices such as heat exchangers and the like. During assembly of a heat exchanger, the tubing may be inserted into openings in a plurality of spaced-apart thin metal sheets forming fins. The openings in the fins typically have a diameter that is slightly greater than the outside diameter of the tubing to facilitate assembly of the tubes with the fins. The tubing is then expanded to form a tight interference fit between the tubing and the fins.

Machines have been developed to expand and permanently deform metal tubing. For example, the tube may be expanded by pushing a ball or other forming tool into the open end of the tubing. The ball has an outer diameter that is equal to the desired final inner diameter of the expanded portion of the tube. The final inner diameter is chosen to provide a tube outer diameter that will provide an interference fit. In this type of operation, the ball or other expanding/forming tool component is mounted on a rigid rod or the like, and the ball is pushed into the open end of the metal tubing while the metal tubing is held in place. This operation thereby puts the metal rod and the tubing into compression.

BRIEF SUMMARY OF THE INVENTION

One aspect of the present invention is a machine and method for forming metal tubing or the like. The machine includes one or more elongated flexible members (e.g. cables) that are wound onto drums. Expanding forming tools such as a mandrel and expanding collet are located on an end of each cable. The expanding forming tools are inserted into open ends of the metal tubes that are to be expanded. The cables unwind from the drums until the expanding end tools (e.g. expanding collets) are at their desired final position. The collets are then expanded by pulling on the cables to shift the mandrels relative to the expanding collets. Outer sleeves of the cables transmit forces pushing on the expanding collets in a direction opposite the pulling forces acting on the mandrels. The expanded collets are then pulled through the tubes utilizing the cables. The cables are wound back onto the drums as the expanded forming tools are pulled through the tubes.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an exploded isometric view of a tube forming machine according to one aspect of the present invention;

FIG. 2 is a right side elevational view of the tube forming machine of FIG. 1;

FIG. 3 is a cross-sectional view of the tube forming machine taken along the line B-B;

FIG. 4 is a top plan view of the tube forming machine of FIG. 1;

FIG. 5 is an enlarged partially fragmentary isometric view of a portion of the tube forming machine of FIG. 1;

FIG. 6 is an isometric view of a drum, tension arm, and tube-forming components;

FIG. 7 is an enlarged isometric view of the tube forming components of FIG. 6;

FIG. 8 is a cross sectional view of an expandable forming tool according to another aspect of the present invention;

FIG. 9 is an isometric view of the collet of FIG. 8;

FIG. 10 is a cross sectional view of a forming tool according to another aspect of the present invention;

FIG. 11 is a cross sectional view of a tube forming machine according to another aspect of the present invention;

FIG. 12 is a top plan view of the tube forming machine of FIG. 11; and

FIG. 13 is a partially fragmentary view of a portion of the tube forming machine of FIG. 11.

DETAILED DESCRIPTION

For purposes of description herein, the terms “upper,” “lower,” “right,” “left,” “rear,” “front,” “vertical,” “horizontal,” and derivatives thereof shall relate to the invention as oriented in FIGS. 1-3. However, it is to be understood that the invention may assume various alternative orientations, except where expressly specified to the contrary. It is also to be understood that the specific devices and processes illustrated in the attached drawings, and described in the following specification are simply exemplary embodiments of the inventive concepts defined in the appended claims. Hence, specific dimensions and other physical characteristics relating to the embodiments disclosed herein are not to be considered as limiting, unless the claims expressly state otherwise.

With reference to FIGS. 1-4, a tube forming machine according to one aspect of the present invention includes a support structure such as a frame 2 and vented side panels 4. A plurality of pull members such as pulleys 6 are rotatably supported on bearings 8 (FIG. 3) that are mounted to the frame 2. A powered actuator such as an electric motor 10 drives a gear 11 that engages a drive gear 9 to thereby provide powered rotation of a main shaft 7. Machine 1 may include a controller 69 that is operably connected to a control panel 70 having one or more switches, buttons, displays, and the like to provide for user input. Controller 69 may also be operably connected to the electric motor 10 to provide for controlled rotation of drums 6.

First end portions 13 (FIG. 4) of cables 14 are wound onto pulleys 6. In the illustrated example, the machine 1 includes eight pulleys 6 and eight cables 14 corresponding to the four upper straight tube portions 16 and the four hairpin tube sections 17 (FIG. 5). In the illustrated example, heat exchanger 66 includes a total of sixteen tube sections. Eight tube sections can be formed in one forming operation utilizing eight cables 14. The heat exchanger 66 is then flipped over and the other eight tube sections can then be formed. It will be understood that the number of pulleys 6 and cables 14 of machine 1 may vary as required for a particular application.

End portions 20 of cables 14 (FIG. 4) extend through openings 21 and 23 in blocks 22 and 23, respectively. Blocks 22 and 24 are supported on support structure or frame 2 by a support plate 25. A feed roller assembly 30 includes upper and lower feed rollers 26A and 26B that are rotatably mounted to upper and lower supports 27 and 28, respectively.

With further reference to FIGS. 6 and 7, the end 34 of each cable 14 includes a mandrel 35 that is connected to elongated flexible inner cable member 36. The inner cable members 36 are movably disposed within cable casings or outer sleeves 37. The mandrels 35 are received within expanding collets 38. Inner ends 40 of expanding collets 38 bear against fittings 41 that are secured to the outer sleeves 37. Expanding collets 38 include a plurality of elongated slots 45 that extend to the outer end 47 of each collet 38 to form flexible fingers 45 that are attached to inner end 48 of collet 38 in a cantilevered manner. Mandrel 35 includes a generally cone-shaped outer surface 42 directly adjacent the head 50 of the mandrel 35. If a sufficient tension force is applied to cable 36 while a compressive force is applied to outer sleeve 37, mandrel 35 is pulled into collet 38, and outer surfaces 42 of mandrel 35 engage tapered inner surfaces 43 of each finger 46 of expanding collet 38. This causes the fingers 46 to flex outwardly, thereby increasing the diameter of curved forming surfaces 51 of collets 38.

Mandrel 50 may be threadably connected to a fitting 52 that is secured to cable 36. In this way, the mandrel 50 and collet 38 can be changed if the mandrel 35 and/or collet 38 become worn or damaged, or if a different size mandrel 35 and collet 38 is required for a particular application.

It will be understood that the cables, mandrels, and expanding collets are simply examples of elongated flexible members and expanding tools that may be utilized according to the present invention. Various elongated members such as chains, a long single strand of flexible matter or the like may also be utilized. Virtually any elongated tension member that can be curved for binding on a drum or the like could be used. Also, various expanding forming tools could be utilized, and the mandrel and expanding collet described herein are simply an example of a suitable expanding forming tool. Also, it will be understood that in situations wherein the tubes to be formed have first and second opposite open ends, the forming tool could comprise a separate tool that is connected to an end of an elongated flexible member after the elongated flexible member is inserted into the first end of the tube such that the end of the flexible member protrudes from the second end of the tube. In this way, a fixed size (non-expanding) forming tool may be utilized with elongated cables and drums or the like according to other aspects of the present invention.

A tension arm 55 (FIG. 6) is rotatably interconnected with each pulley or drum 6. A key 56 engages a corresponding keyway (not shown) in main shaft 7, such that tension arm 55 rotates with main shaft 7. Arm 55 extends through a slot 58 in body 59 of drum 6, and a pair of plates 57 form a lost motion connection that limits rotational movement of arm 55 relative to drum 6. An outer end 60 of arm 55 is secured to an end 61 of cable 36, and an inner end 62 of outer sleeve 37 is secured to a fitting 63 on drum 6. Thus, angular movement of tension arm 55 within slot 58 of drum 6 causes cable 36 to move relative to outer sleeve 37.

During operation, rotation of main shaft 7 causes tension arm 55 to rotate at the same rate as shaft 7. However, drum 6 only rotates if tension arm 55 is in contact with either of the plates 57. Initial movement of arm 55 (without rotation of drum 6) shifts the mandrel 50 relative to expanding collet 38 to thereby expand or contract collet 38. Upon further rotation, the arm 55 contacts one of the plates 57, thereby causing both the cable 36 and the outer sleeve 37 to move at the same rate.

A heat exchanger 66 (FIG. 5) includes a plurality of thin plate-like metal fins 67 having preformed circular clearance openings 68. Metal tubes 16 and 17 are inserted into openings 68. Initially, the openings 68 in fins 67 are slightly larger than the outer diameters of tubes 16 and 17 such that the tubes 16 and 17 can be readily inserted into the openings 68 of fins 67 to thereby provide an initial assembly of heat exchanger 66.

Heat exchanger 66 is then positioned adjacent the ends 34 of cables 14. Heat exchanger 66 may be held in place manually or it may be secured to a support surface or fixture (not shown) adjacent the machine 1. Machine 1 is then actuated, and drums 6 and feed rollers 26A and 26B move the ends 34 of cables 14 into the open ends 65 of tubes 16 and 17.

After the ends 34 of cables 14 are fully inserted into the tubes 16 and 17 (i.e. the ends 34 are positioned beyond the outermost fin 67), tension arm 55 is rotated relative to the drum body 59 to thereby tension cable 36. This pulls mandrel 50 into expanding collet 38, thereby causing the curved forming surfaces 51 of collets 38 to expand outwardly. Outward expansion of collet 38 generates an outward force on tubes 16 and 17, thereby expanding the diameter of the tubes 16 and 17. The tubes 16 and 17 are made of copper or other formable metal, such that expansion of collet 38 permanently deforms the tubes 16 and 17.

After the collets 38 are expanded due to movement of tension arm 55 relative to drum body 59, the drums 6 are rotated to pull the ends 34 through the tubes 16 and 17 in the direction of the arrow “S” (FIG. 4). The ends 65 of the tube section 16 and 17 bear against outer surface 72 of guide block 24 or other suitable surface to thereby put the tube section 16 and 17 into compression to balance the force caused by tension on cables 14 as the expanded collets 38 are moved through the tubes 16 and 17. Alternately, the outer ends of the tubes 16 and 17 may be retained by clamps or the like (not shown), such that the tubes 16 and 17 are in tension as the expanded collets 38 are pulled through the tubes 16 and 17. Oil or other lubricant may be placed on the collets 38 prior to insertion into tube 16 and 17, or lubricant may be sprayed or otherwise positioned inside the tubes 16 and 17 to facilitate the forming process.

The size of the collets 38 and mandrel 35 are selected to permanently expand the outer diameters of tubes 16 and 17 sufficiently to create an interference fit between the tubes 16 and 17 and openings 68 in fins 67. In general, the tubes 16 and 17 are deformed both elastically (i.e. temporarily) and plastically (i.e. permanently), such that the diameter of the tubes 16 and 17 is typically reduced slightly after the collets 38 pass through the tubing 16 and 17. Thus, the expanded diameter of the collets 38 may be slightly larger than the final desired inner diameter of the tube 16 and 17 to account for the elastic contraction of tubes 16 and 17.

After the expanding collets 38 are pulled out of the open ends 65 of tubes 16 and 17, the fittings 41 contact a travel plate 75, thereby shifting the tension arm 55 relative to drum body 59. This causes a compressive force to be applied to cable 36 to push the mandrels 35 out of the collets 38. This causes the collets 38 to shrink in diameter for insertion into the tubes of the next heat exchanger 66 to be formed.

Because the cables 14 wind onto drums 6, the forming machine 1 has a compact overall size that is much smaller than that of rigid pushrod type forming machines. The machine 1 may be utilized to form tubing of different lengths by adjusting the length of cable 14 that is unwound from drums 6. Also, mandrels and/or collets of different sizes may be utilized to form tubing of various sizes as required for a particular application.

With further reference to FIG. 8, an expandable forming tool 34A according to another aspect of the present invention includes a fitting 78 that is securely connected to an end 80 of a cable 82. Cable 82 comprises an elongated flexible member that may be similar to inner cable member 36 described in more detail above. However, cable 82 does not include an outer cable casing or sleeve 37. Fitting 78 includes a first connecting portion 84 having a connector 85 that securely connects the fitting 78 to end 80 of cable 82. Fitting 78 also includes a second connecting portion 86 that is received in a passageway 90 of collet 88. Fitting 78 includes a first annular surface 92 that is configured to engage end surface 94 of collet 88 to thereby limit travel of collet 88 in the direction of the arrow “A” relative to fitting 78. Fitting 78 includes a second annular surface 96 that generally faces a third annular surface 98 of collet 88. A coil spring 100 is disposed on second elongated end portion 86 of fitting 78 between the second and third annular surfaces 96 and 98 to thereby bias the collet 88 in a direction opposite the arrow A relative to fitting 78. A mandrel 135 includes a threaded bore 104 that threadably engages a threaded end portion 102 of fitting 78 to thereby connect mandrel 135 to fitting 78. Mandrel 135 includes cone-shaped outer surface 142 that is configured to engage a tapered inner surface 143 of collet 88. With further reference to FIG. 9, collet 88 includes a plurality of elongated slots 45 forming elongated fingers 46 that flex outwardly as mandrel 135 is shifted in the direction of the arrow A relative to collet 88 to thereby expand the diameter of forming surfaces 51 of collet 88.

With further reference to FIG. 10, a forming tool 110 according to another aspect of the present invention comprises a ball-shaped end 112 having smoothly-curved outer forming surfaces 114, and a threaded connector 85 that removably connects forming tool 110 to end 80 of cable 82. Outer forming surface 114 may be spherical or oblong. The ball-shaped end 112 may be made from a solid piece of metal (e.g. tool steel) or other suitable material. Thus, in contrast to expandable collets 38 and 88, forming tool 110 is not expandable.

In use, forming tool 110 is detached from end 80 of cable 82, and end 80 of cable 82 is inserted into an open end 65 (FIG. 4) of a straight tube 16, and electric motor 10 is the actuated to unwind cable 82 from drum 6. After end 80 of cable 82 extends out of open end 71A of tube 16, electric motor 10 is turned off to stop further unwinding of cable 82. Forming tool 110 is then attached to end 80 of cable 82, and electric motor 10 is actuated to pull forming tool 110 back through tube 16. The forming surfaces 114 of forming tool 110 have a dimension (e.g. diameter) that is greater than an initial (i.e. unformed) inner diameter or tube 16, such that forming surfaces 114 cause tube 16 to deform and expand outwardly, thereby causing a tight interference fit of tube 16 in openings 68 of fins 67. Forming tool 110 can be detached from end 80 of cable 82 after forming tool 110 is pulled back out of open end 65 of tube 16, and the forming process can be repeated. If required, a plurality of forming tools 110, cables 82, drums 6, and related components may be utilized to simultaneously form a plurality of tubes 16.

With further reference to FIGS. 11 and 12, a tube forming machine 155 according to another aspect of the present invention includes a support structure 156, and a powered drive assembly 158 that is mounted to the support structure. The powered drive assembly 158 includes an electrical servo motor 160 that drives a toothed belt 162 via a toothed cog or pulley 164. Belt 162 engages a cog or pulley 166 that is fixed to a shaft 168. A plurality of drums 170 are mounted to the shaft 168, such that drums 170 rotate upon actuation of electrical servo motor 160. With further reference to FIG. 13, each drum 170 includes outer clam shell halves 172 (see also FIG. 12), and an inner drum 174 having a cylindrical outer surface 176. Cables 82 extend through a gap 178 formed between adjacent outer drum halves 172 and wrap onto cylindrical outer surface 176 of inner drum 174. The outer drum halves 172 clamp onto cable 82. In use, the threaded fasteners 180 can be loosened to unclamp drum halves 172 from cable 82, and extra cable 82 can be extended from inner drum 174. Similarly, cable 82 can be shortened by winding extra cable onto inner drum 174. After adjusting the length of the cable 82, the threaded fasteners 180 can be retightened to clamp cable 82. In this way, each of the forming tools 34A (FIG. 12) can be positioned such that they enter the open ends 182 of tubes 184 at substantially the same time.

Tube forming machine 155 includes a guide roller 188 (FIGS. 11-13) that is mounted adjacent to the drums 170 to movably support the cables 82. Machine 155 also includes a plurality of guide tubes 186 that are mounted to support structure 156 by support block 190. The guide tubes 186 have flared open ends 192 adjacent guide roller 188. “Downstream” end 194 of tubes 86 are positioned adjacent a pair of pinch rollers 196A and 196B. A pulley 195 is mounted to servo motor 199, and drives a flexible belt 197. The flexible belt 197 drives the pinch rollers 196A and 196B. A belt tensioning device 200 provides for tensioning of belt 197. In use, the pinch rollers 196A and 196B drive the cable 82 to thereby push the forming tools 34A through the tubes 184. The pinch rollers 196A and 196B are preferably driven at a slightly higher rate than the drums 170 to thereby create tension on the cables 82 in the area between pinch rollers 196A and 196B and the drums 170. In general, some slippage between pinch rollers 196A and 196B and the cables 82 will occur due to the differences in the drive rates.

A plurality of guide tubes 202 are mounted to support structure 156 by brackets 204 and support blocks 206. Guide tubes 202 include a flared outer end 208 that is positioned adjacent a guide block 210. The guide block 210 supports the expandable forming tubes 34A as they are inserted into the open ends 182 of tubes 184. The guide tubes 202 support the cables 82 and prevents collapse of the cables 82 as the forming tools 34A are driven into the tubes 184.

In use, the heat exchanger tubes and fins 184 are positioned on a fixture 212 (FIG. 11). The fixture 212 is configured to retain the tubes 184 and fins 185 of the heat exchanger, and may be configured to support specific heat exchangers. Once the tubes 184 and fins 185 are secured in fixture 212, the heads 150 of mandrels 135 are aligned with open ends 182 of tubes 184 16 or 17. Machine 155 may include an operator input touch screen 214 (FIG. 12) or other suitable input feature. The machine 155 may also include a controller 216 that is operably connected to the input screen 214 and powered drive assembly 158 and drive assembly 198. The controller 216 is configured to drive the cables 82 a selected distance based on a user input utilizing touch screen 214. In use, a user inputs the desired travel distance for forming tools 34A based on the length of tubes 184. The drums 170 and pinch rollers 196A, 196B then drive the cables 82, causing the forming tools 34A to be driven into the tubes 184. The open ends 182 of the tubes 184 contact forming surfaces 51 of collet 88, thereby moving collets 88 in the direction of the arrow A, causing spring 100 to compress. First annular surface 92 of fitting 78 may contact end surface 94 of collet 88 to thereby prevent further movement of collet 88 relative to fitting 78.

Controller 216 then actuates drive assemblies 158 and 198 to thereby cause the cables 82 to wind onto drums 170. As cables 82 are retracted, frictional contact between surfaces 151 of collet 88 and tubes 184 causes collet 88 to shift in a direction opposite the arrow A (FIG. 8). Coil spring 100 also generates a force tending to shift collet 88 in a direction opposite the arrow A relative to fitting 78. As the collet 88 shifts in a direction opposite the arrow A, the cone shaped outer surface 42 of mandrel 35 engages inner surface 143 of collet 88, thereby causing fingers 46 to flex outwardly to increase the diameter of forming surface 151. As the collets 88 are pulled through the tubes 184, the diameters of the tubes are expanded due to contact between forming surfaces 51 and the inner side wall surfaces of tubes 184. This causes the tubes 184 to become tightly engaged with the openings in fins 184 of the heat exchanger.

As the drums 170 continue to rotate, the collets 88 are eventually pulled out of the open ends 65 of tubes 184. The heat exchanger can then be removed and new tubes 185 and fins 186 can then be positioned on fixture 212, and the forming tools 34A can then be inserted into the open ends 182 of tubes 184 to repeat the forming operation.

The present invention is not limited to the specific example described above. For example, various mechanisms and devices may be utilized to pull on the cables, and to provide an expanding portion that is pulled through the tubes. Also, various types of elongated flexible members could be utilized in place of the cable arrangement described above, and other expanding and retracting forming devices or tools could be utilized in place of the mandrel and expanding collet described above. Still further, although a circular drum is preferred for winding the cable, other storage devices and arrangements could be utilized to provide for storage of an elongated flexible unit in a relatively compact manner.

It is to be understood that variations and modifications can be made on the aforementioned structure without departing from the concepts of the present invention, and further it is to be understood that such concepts are intended to be covered by the following claims unless these claims by their language expressly state otherwise. 

What is claimed is:
 1. A tube forming apparatus, comprising: a support structure; a winding member rotatably mounted to the support structure; at least one elongated flexible member that winds onto the winding member, the elongated flexible member having an end that moves towards the winding member upon rotation of the winding member; a powered actuator operably connected to the winding member such that actuation of the powered actuator causes the winding member to rotate and wind the at least one elongated flexible member onto the winding member; an expandable forming tool connected to the end of the at least one elongated flexible member, the expandable forming tool having outer forming surfaces that can be selectively shifted outwardly from an insertion configuration to a forming configuration, and wherein: the end of the elongated flexible member and the expandable forming tool can be inserted into an elongated metal tube in the insertion configuration, followed by shifting the outer forming surfaces outwardly, followed by actuation of the powered actuator to rotate the winding member to pull the expandable forming tool back through the metal tube, such that the tube is deformed outwardly due to contact between the outer forming surfaces of the expandable forming tool and inner surfaces of the tube.
 2. The tube forming apparatus of claim 1, wherein: the expandable forming tool comprises an outer member, wherein the outer forming surfaces are disposed on the outer member; and wherein: the expandable forming tool further comprises an inner member at least partially disposed in the outer member, and wherein the inner member is configured to engage the outer member and shift the outer forming surfaces outwardly.
 3. The tube forming apparatus of claim 2, wherein: the outer member includes a plurality of flexible fingers, wherein the outer forming surfaces are disposed on the fingers.
 4. The tube forming apparatus of claim 3, wherein: the outer member includes a base portion, and the fingers extend from the base portion.
 5. The tube forming apparatus of claim 2, wherein: the inner member comprises a mandrel having an inner end and an outer end that is enlarged relative to the inner end, the inner member further comprising a tapered transition portion extending between the inner end and the outer end.
 6. The tube forming apparatus of claim 5, wherein: the tapered transition portion has a generally conical outer surface.
 7. The tube forming apparatus of claim 6, wherein: the outer member includes inner surface portions that engage the conical outer surface of the inner member.
 8. The tube forming apparatus of claim 7, wherein: the inner surface portions of the outer member are generally conical and slidably engage the generally conical outer surface of the inner member as the inner member is shifted axially relative to the outer member.
 9. The tube forming apparatus of claim 2, wherein: the outer member defines a bore extending axially through the outer member; the inner member is movably disposed in the bore, the inner member including a tapered outer surface that engages the outer member and moves the outer forming surfaces outwardly upon shifting of the outer member relative to the inner member in a first direction; and including: a resilient member biasing the outer member in the first direction relative to the inner member.
 10. The tube forming apparatus of claim 1, wherein: the elongated flexible member comprises a cable.
 11. The tube forming apparatus of claim 10, wherein: the cable includes an inner strand and an outer casing, wherein the inner strand is movably disposed in the outer casing; and wherein: the inner strand and the outer casing are operably connected to the expandable forming tool such that shifting of the inner strand relative to the outer sheath causes the outer forming surfaces of the expandable forming tool to shift outwardly.
 12. The tube forming apparatus of claim 11, wherein: the winding member comprises a pulley disposed on the shaft for rotation relative to the shaft; and including: a shaft rotatably mounted to the support structure; a lost motion device including a tensioning member that is fixed to the shaft, wherein the tensioning member permits rotation of the winding member in first and second opposite directions relative to the shaft for a predefined rotational distance, after which the pulley rotates with the shaft; and wherein: the tensioning member is connected to the inner strand and the outer casing is connected to the pulley such that rotation of the pulley relative to the shaft shifts the inner strand relative to the outer casing to thereby selectively shift the outer forming surfaces inwardly and outwardly.
 13. The tube forming apparatus of claims 12, wherein: the pulley includes spaced apart stop surfaces; the tensioning member comprises a tension arm disposed between the stop surfaces and defining a gap relative to at least one of the stop surfaces.
 14. A tube forming apparatus, comprising: at least one elongated flexible member; a powered device operably connected to the elongated flexible member, wherein the powered device includes a pull member that is operably connected to the elongated flexible member and a powered actuator that is operably connected to the pull member such that actuation of the powered actuator causes the pull member to pull on the elongated flexible member; and a forming tool connected to the elongated flexible member, the forming tool having outer forming surfaces configured to slidably engage an inner surface of a side wall of a tube to thereby expand the tube outwardly to increase an outer dimension of a tube as the forming tool is pulled through the tube.
 15. The tube forming apparatus of claim 14, wherein: the outer forming surfaces of the forming tool can be shifted outwardly to increase a size of the forming tool.
 16. The tube forming apparatus of claim 15, wherein: the forming tool includes an outer member having a bore therethrough, and an inner member movably disposed in the bore, the inner member having an engagement surface that engages the outer member upon movement of the inner member relative to the outer member to shift the outer forming surfaces outwardly, and wherein the inner member is connected to the elongated flexible member such that tension on the elongated flexible member causes the inner member to shift relative to the outer member and thereby shift the outer forming surfaces outwardly.
 17. The tube forming apparatus of claim 14, wherein: the pull member comprises a pulley, and the powered actuator comprises an electric motor that rotates the pulley and causes the elongated flexible member to wind onto the pulley.
 18. The tube forming apparatus of claim 14, wherein: the elongated flexible member defines an end; the forming tool is detachable connected to the end of the elongated flexible member, the forming tool comprising a rigid, non-expandable member having smoothly curved outer forming surfaces.
 19. The tube forming apparatus of claim 18, wherein: the outer forming surfaces are approximately spherical.
 20. A method of expanding a tube, the method comprising: providing an elongated metal tube having an open end and inner and outer surfaces defining inner and outer diameters, respectively; providing a powered machine including a powered actuator and an elongated flexible member that can be pulled upon actuator of the powered actuator, the powered machine including an expandable forming tool connected to the elongated flexible member, the expandable forming tool having outer forming surfaces that can be shifted outwardly from a first configuration to a second configuration; inserting the expandable forming tool into the open end of the elongated metal tube; pushing the elongated flexible member to move the expandable forming tool in the tube in a first direction; causing the expandable forming tool to shift from the first configuration to the second configuration, wherein the outer forming surfaces define an outer dimension that is transverse to a length of the tube, and wherein the outer dimension is greater than the inner diameter of the tube; deforming the elongated metal tube to increase the diameter of the elongated metal tube by pulling the expandable forming tool back through the elongated metal tube in a second direction that is substantially opposite the first direction with the outer forming surfaces pushing outwardly on the inner surface of the elongated metal tube.
 21. The method of claim 20, wherein: the outer forming surfaces slidably engage the inner surface of the elongated metal tube as the expandable forming tool is pulled in the second direction.
 22. The method of claim 20, wherein: the elongated metal tube has a hairpin shape and includes a pair of generally parallel linear sections that are joined by a curved portion; and including: providing a plurality of plate members, each having at least two openings therethrough; positioning the elongated tube such that the linear sections extend through the two openings prior to pulling the expandable forming tool through the tube in the second direction.
 23. The method of claim 20, wherein: the expandable forming tool includes an outer member and an inner member that movably engages the outer member; and including: shifting the inner member relative to the outer member to thereby shift the outer forming surfaces from the first configuration to the second configuration.
 24. The method of claim 20, wherein: the elongated metal tube is substantially linear with opposite ends that are open; and including: providing a plurality of plate members, each having at least one opening therethrough; positioning the elongated metal tube in the openings prior to pulling the expandable forming tool back through the elongated metal tube in the second direction. 